#include <stdio.h>

int main()
{
    char a = -1;
    //1111 1111
    //整型提升
    //1111 1111 1111 1111 1111 1111 1111 1111
    //取反加一
    signed char b = -1;

    unsigned char c = -1;
    //1111 1111
    //整型提升
    //0000 0000 0000 0000 0000 0000 1111 1111
    printf("a=%d,b=%d,c=%d", a, b, c);
    printf("a=%u", a);

    return 0;
}